Ras,

You're describing what I've known as "green lining".
Materials *could* involve a printout of schematic, a net
list, a bom, fab drawings for all layers of the board, a
light table and a green pencil.  Tape all the fab drawings
at the top of the sheet onto the light table so you can
flip through the drawings like a book.  All fab drawings
are taped down so the regristration marks line up as if
to make a "paper" version of the board.  Two people are
needed.  One to call out a starting point and an ending
point with the schematic or netlist.  The other is for
verification of the start and end points on the fab
drawings with the pencil drawing over the traces until
all are done.

Depends upon the philosophy of the company and the situation.

I worked in one company where an electrical designer who would
not release any drawings until this procedure had been done.
Small company.  Needed as few mistakes as possible. The
gentleman in question was extremely confident in his design
and wanted "all the bases covered".  As a consequence, very
few mistakes were made by either him or the board house.
It also taught me about involving people in the communication
side of things with a project.

Another small company where I worked didn't want anything
to do with greenlining and incurred all the responsibility
onto the board house. Mistakes were made by both sides.
They gave no indication they wanted to change.  And they
discouraged green lining sayin it was a waste of time.
I did it any way. And we corrected some layout concerns
and mistakes.

I guess it depends upon the consequences of making just
one mistake or the complexity of the board.  Small runs
with no urgency - maybe not needed.  High urgency or
large numbers of boards where on mistake might spell the
difference between a "stop ship" or trashing 1,000 new boards
would make me think twice before putting my name on the line.

I'm speaking from the customer side of things here.

Backplanes can be tricky.  Doing a green line of a high
speed design might let someone see something that would
raise an eyebrow or two in layout even though it's done
according to the schematic.

That's my 2.5 cents worth.

Regards,  Doug


Ras Huang wrote:
>
> Dear fellows:
>
> We are designing a backplane for a high-speed transmission telecom
> equipment.  The highest speed running on this backplane is 155Mbits/sec.
> My colleague who has a little experience of designing a previous
> backplane used in a lower speed one suggests me that, a pre-layout by
> manual (paper and pencil) absolutely necessary for having a trace check
> before being submitted into real layout.  Anyway, I don't think it is a
> good idea because it takes too much efforts, unfortunately, I am agree
> with that a pre-check is needed but I don't know is there any better
> way?
>
> Anyway comments from you?

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